If you simply must use an Amiga keyboard, there is this rather unelegant solution:
The Mikronik A1200 keyboard chassis converts the A1200 keyboard into a PS/2 keyboard that can be plugged straight into any PC.
Apparently the adapter only supports one keypress at a time.
And you probably wont find one anywhere. 
Actually I think I still have a Micronik keyboard housing somewhere in a box with the adapter circuit included. IIRC only the cable is deceased. I put it on E-Bay or some such many moons ago, but nobody wanted it for any price..
